The structure, expression, and evolution of crystallin genes of vertebrates and invertebrates are being studied. Cis-acting control elements for lens expression have been identified in alpha- and beta- crystallin genes. Unexpectedly, the alphaA-crystallin elements are occupied in both expressing and nonexpressing cultured cells. Footprint analyses have shown that alphaB-crystallin gene expression in lens and muscle involves a combination of shared and tissue- specific cis-elements. Two promoters are used in a tissue-preferred fashion for expression of the alphaB-crystallin gene; a strong muscle/weak lens enhancer is present between these promoters. This enhancer uses a muscle regulatory factor (MRF) site exclusively for muscle expression and at least two other sites for lens and muscle expression. Transgenic mouse and transfection experiments have shown that the alphaA- crystallin cis-acting elements are functionally redundant. A trans- acting factor (alphaA-CRYBP1) important for expression of the mouse `A-crystallin gene was shown unequivocally to bind to its cognate cis-element. Immunoblotting experiments indicated that this factor exists in different overlapping sizes in different tissues, and the promoter for its gene has been cloned and expressed in transfected lens cells. The two delta-crystallin genes were shown to be under tissue-specific and developmental regulation. Crystallin recruitment in the squid was shown to differ from that in vertebrates in that the parental enzyme gene (glutathione S-transferase) gave rise to a related family of crystallins without enhancing its own lens expression. The ALDH-like crystallin cDNA of cephalopods has been cloned and sequenced. Cloning of the three J1-crystallin genes of cubomedusan jellyfish showed that they lack introns, encode novel proteins, and have surprisingly diverse 5' flanking sequences.